OBSERVATIONS AND EXPERIMENTS ON EUGLENOIDINA. 173 



VI. Euglenoids of Species A in Toad Tadpoles. A large number 

 of toad tadpoles were collected from one of the large ponds at the 

 fish hatchery on June 12, 1922. Their average measurements 

 were: total length, 20 mm.; body, 8 mm.; tail, 12 mm.; hind 

 legs, 3 mm.; intestine, 47 mm.; rectum, 9 mm. They were kept 

 in the laboratory in a flat dish without change of water but with 

 the addition of fresh water from time to time to compensate for 

 evaporation. Some of the tadpoles developed fore legs and ac- 

 quired the characteristics of the young toad within a few days; 

 these apparently had reached a stage when no more food was 

 necessary to bring this about. In most of them, however, growth 

 and metamorphosis were inhibited by the condition of starva- 

 tion to which they were subjected. Specimens were examined at 

 intervals w r ith the results presented in Table Y '. The following 



TABLE V. 



NUMBERS OF EUGLENOIDS OF SPECIES A IN THE RECTUM OF TOAD TADPOLES 



COLLECTED ON JUNE 12, 1922, AND KEPT WITHOUT FOOD. 

 For method of counting see text. 



observations seem worthy of mention, (i) The incidence of in- 

 fection with Species A was 100 per cent. (2) No encysted or 

 dividing specimens were encountered. (3) Most of the eugle- 

 noids were swimming freely or undergoing metabolic movements ; 

 a few were spherical or pear-shaped. (4) The number of speci- 

 mens was not diminished or increased by the starvation of the 

 host. (5) Evidently Species A is a "normal" inhabitant of the 

 rectum of toad tadpoles in this locality. (6) A decided decrease 

 in the intensity of the green color of the chromatophores was 

 noticeable in almost all specimens; some were pale green and 

 others were almost colorless. This condition probably resulted 

 from lack of light and may be contrasted with that observed in 

 the case of specimens from starved tadpoles of Rana pipiens. 



